The Whitworth had the hex groove barrel as I remember. I just looked up the Creedmore. And Pedersoli mold states it shot a 500 grain .451 conical bullet, with 65 grains of FFF powder. They have a 1-21 twist. I find that very interesting as it is basically the same caliber and twist as my White Model 97 .451. And I shoot a .460 grain conical with 65 grains of Triple Seven powder.